Problem: Setup H1 and C13 by using standard parameters, there is no signal. Just noise line.


1. Use scope to check channel A input pulse: (pw 40us, tpwr=56, d1=0.5 aq=0.5 gain=0)

There is an input pulse.

2. Use scope with a 30dB attenuators to check channel A output. There is no output pulse.

Amplifier problem!!!!!!!!!!!!!!!!!?

Take it out and check it.


BNC connectors: top right channel A and top left channel B? (INPUT low power pulse > 1 Volts)

N-type connect: bottom right H1 pulse output, left X pulse output.

25 pin connector to the front Amp & Rout board (exchangeable with other inova system)

Power supply 220Volts. Use the console power supply!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

25 pin ribbon cable connects to the top of the board.


Step 2:? Open the amplifier box.

1. Measure the 28 VDC to the amplifier (High Band). No voltage! It is suggested that the power supply has problem.

2. Measure the power supply, from the two big capacitor, there is +66V.


3. Check the heatsink assambly (Aluminum box one left) There are two connectors. Unplug them.

There is a snaper U602S (it is overheat resistant. It is OPEN at normal operation, if it is overheated, it will close and cut off the power

supply to the amplifier). Use voltmeter to measure it. It is OPEN. But no 28Volts output.



1. The transistors(MJ15001NPN) on this board are bad. MJ15001 could be purchased from Electronic distribution stores.,4450,MJ15001,00.html

Parametric Table
Orderable Part IC Max (A) VCEO(sus) Min (V) hFE Min hFE Max fT Min (MHz) PTM Max (W) Polarity Package Packing
MJ15001 15 140 25 * 150 * 2 200 NPN TO3 Tray
Orderable Devices
Product Status Package Container Budgetary Price/Unit Action
Type Pins Case Outline Type Qty.
MJ15001 Active TO-204 (TO-3) 2 Tray 100 $1.92
  • High Safe Operating Area (100% Tested) - 5.0 A @ 40 V
    0.5 A @ 100 V
  • For Low Distortion Complementary Designs
  • High DC Current Gain - hFE = 25 (Min) @ IC = 4 Adc



2. The blanking signals are not correct.

These small wires are blanking signals from the amplifier control board.

There is no diagram from AMT or Varian. It is very hard to trace the signal without diagram.

However, it could be purchase from AMT for about $450/each.


After replace the amplifier control board, 28V is restored. It is working.



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